En is used for words that are common gender. Ett is used for words that are neuter gender. You won't be able to tell which is used for a word, just by looking at the word. That's why, when you learn new words, you also have to memorize the article associated to it. For example:
En tidning - A newspaper.
Ett brev - A letter.
As you can see, the two words en and ett, mean exactly the same thing, so that means you have to memorize which words use en and which ones use ett. You can also find more info under the Tips and Notes of Basics 1. Hope that helped!
The word is one syllable, but we should be aware that, according to this video on the Swedish vowels https://www.youtube.com/watch?v=hzYArZVTD4s&t=2m12s, it is common for the Swedish long e to end in a weak schwa /ə/.
The v sound at the end of this word is so unclear. I checked a few other sources online and they all pronounce the “v” sound at the end of the word (this sounds more like a 2 syllable word with an r or n at the end). I wish I could tell if this is just a poor robo-voice issue or a genuine way to renounce the word.